<i>Petunia hybrida</i> のはい珠培養における鉄, ホウ酸, および糖が発芽種子数におよぼす影響

Abstract

The present investigation deals with in vitro growth of ovules on a half of the placenta of Petunia hybrida, W166H×K146BH (each clone is self-incompatible), with special reference to the influence of iron, boric acid, and sugars. The culture medium of NITSCH (1951), modified by the addition of 500mg/l KNO3 and 80mg/l NH4NO3, was used as a basal medium.The optimal initial hydrogen-ion concentration was at pH of 4.5-5.0 in the basal medium and at pH of 6.0 in the basal medium with Fe-EDTA at an iron concentration of ca. 2.5ppm instead of ferric citrate.The number of viable seeds per ovary increased with an increasing concentration of ferric citrate from 10 to 40mg/l in the basal medium. Iron complex Fe-EDTA composed of 50mg/l FeSO4•7H2O and 40mg/l disodium ethylenediaminetetraacetate, dihydrate (Na2-EDTA) was also an effective compound and was favorable for the viable seed production.10mg/l or above boric acid should be added to the basal medium containing either ferric citrate or Fe-EDTA. Medium containing 50mg/l boric acid was superior for the viable seed production to those with any other concentration. The efficancy of boron was influenced by the organic forms of iron. The medium with Fe-EDTA at an iron concentration of ca. 2.5ppm was superior to that with 10mg/l ferric citrate.Basal medium containing 7.5 per cent sucrose or 5 per cent fructose produced the maximal viable seeds and that containing a mixture of sucrose and fructose or sucrose and glucose was inferior to the basal medium.From these results, experiments were conducted to clarify the interaction among three components, iron, boric acid, and sugars. About 5-6 normal seedlings with two cotyledons and roots per ovary were obtained in the medium containing ca. 10 ppm Fe as Fe-EDTA, 25mg/l boric acid, and 7.5 per cent sucrose. This was about six times as the number of seedlings produced in the basal medium.In the basal medium containing fructose instead of sucrose, however, the higher concentrations of boric acid and/or iron failed to bring about the noticeable effect.